SCJP-02 流程控制 11题.doc

8二 流程控制11题 (1) Given the following Java code: 11.12.13.14.15. public static void main (String[] args ) { Object obj = new int [] {1, 2, 3 } int [] someArray = ( int [] ) obj; for ( int x : someArray ) System.out.print(x+ ); }What is the result? (結果為何?) A. 1 2 3B. Compilation fails because of an error in line 12. (因為在第12列的錯誤而編譯失敗)C. Compilation fails because of an error in line 13. (因為在第13列的錯誤而編譯失敗)D. Compilation fails because of an error in line 14. (因為在第14列的錯誤而編譯失敗)E. A ClassCaseException is thrown at runtime. (執行時期會丟出 ClassCaseException ) A 陣列 is-a Object, 所以第12列沒有問題 再將 obj 強制轉型回 int[], 也沒有問題 最後以 foreach 將該陣列值印出, 將會是 1 2 3 () Given the following Java code: 25.26.27.28.29. int x = 12;while ( x10 ) { x--; }System.out.print( x );What is the result? A. 0B. 10C. 12D. Line 29 will never be reached. (第29列不可能執行到) C 一開始準備執行到 while 迴圈 12 10 並不成立, 所以將直接印出 12 (3) Given the following Java code: public static Iterator reverse ( List list ) { Collections.reverse( list ); return list.iterator(); }public static void main(String[] args ) { List list = new ArrayList(); list.add(1); list.add(2); list.add(3); for ( Object obj: reverse(list)) System.out.print(obj + , ); }What is the result? A. 3, 2, 1B. 1, 2, 3C. Compilation failsD. The code runs with no output. (本程式碼執行, 不會有任何輸出)E. An exception is thrown at runtime C 題目中的 for 迴圈是寫成 foreach 語法. 但是 reverse() 其傳回執型態為 Iterator, 並非陣列型態或是 java.util.Collection 型別 其實, 若要探究根源, 就是只要有 implements java.lang.Iterable 的介面, 就可以使用 foreach 語法將其元素取回. java.util.Collection 介面之父介面就是 java.lang.Iterable 而 java.util.Iterator 介面並非 java.lang.Iterable 所以將會產生編譯時期的錯誤 (4) Given the following Java code: 11. 12.13.14.15.16.17.18.19.20. public static void main( string[] args ) { String str = null; if( str == null ) { System.out.println(null); } else ( str.length() == 0 ) { System.out.println(zero); } else { System.out.println(some); } }What is the result? (結果為何?) A.B.C.D.E. nullzerosomeCo